I think that he's referring to this: https://www.jpx.co.jp/english/derivatives/products/interest-rate/3m-tona-futures/index.html
I tried searching TONAR futures from Esignal charting s/w (which is very comprehensive) but I couldn't find it. I think OP is talking about the new SONAR futures. TONA SONAR TONAR are very different though they have some common characters. Many people expect IB to offer everything under the sun and moon. Poor IB; beaten left and right.
I went to the jpx.co.jp website and used their search engine for TONAR. Besides TONAR also SONAR and other interest rates related products appeared in various documents there. Multiple fancy names have been invented in order to no longer use LIBOR ...
I searched TONAR from Esignal. It is classified as a bond, not Futures. description : Yen uncollateralized O/N call rate.